高双折射光纤环镜轴向应变灵敏度研究

摘要

理论推导了高双折射光纤环镜轴向应变灵敏度公式,讨论了在高双折射光纤材料和入射光源不变的前提下,高双折射光纤长度以及作为敏感元件的传感长度与传感器轴向应变灵敏度的关系,讨论了入射光源相同时高双折射光纤材料与传感器轴向应变灵敏度的关系.结果表明:在高双折射光纤材料和入射光源不变的前提下,高双折射光纤环镜波长变化与轴向应变成线性关系,线性灵敏度为高双折射光纤材料和入射光源中心波长决定的常数,与接入的高双折射光纤长度、作为敏感元件的传感长度无关.%By monitoring hyperspectral characteristics of spring maize from jointing to silking stage under different drought stress in Jinzhou of Liaoning, China, its spectral characteristics of visible light, red edge region and near infrared were researched, and the correlation of spectral reflectivity of different wavelength with soil moisture was analyzed. The results show that during the jointing to siking stage, the spectral reflectivity of 350~710 nm has significant negative correlation to soil moisture of 0 and 20 cm depth, but the spectral reflectivity of 710- 300 nm has positive correlation to soil moisture of 0, 20, 40 and 60 cm, and the significant correlation is at 40 cm depth. The spectral reflectivity of red edge region (680~760 nm) which is relatively sensitive and stable, can better reflect the growth status of the plant, and the reflectivity variation per unit wavelength in this region increased at first and then decreased. The trend of polynomial regression curve of red edge parameters and soil moisture of different depth (0~60 cm) is similar, which shows that soil moisture of 0 and 20 cm increased at first and then decreased, but that of 40 cm and 60cm was opposite.